I know it's complicated, but as a general rule of thumb in these cases try to find out if all the unions are involved.

In this case only a minor one (UBS) was, while the major unions (CGIL, CISL, UIL) had called themselves out of it.

I flew back to Milan on the day of the strike and everything was business as usual, possibly better than usual because my flight landed early, luggage arrived quickly and there were three no. 73 buses to city centre waiting outside.